Protective device for electric circuits



Feb.- 2 1926.

T. E. BARNUM ET AL PROTECTIVE DEVICE FOR ELECTRI CRCUITS Filed Feb. 25, w'1922 Bim Patented THOMASl E. BARNUM, C F VJAUW" WISCONSN, ASSIGNURS T T `E CUTL-Sll-HAIQMER MFG. C0., F MILWAUKEE, "WES- CONSIN, A CORPORATION @F "'iFJ'lSCOiSN.

PRTETVE BEVCE FR ELECTRIC CIRCUITS.

Application `filed February To (1N ywhom. it may concern:

I Be it known that We, Trione-is E. Ban- NUM and ERWIN R. Sronniin. citizens ot the `United States, residing, respectively7 at lllauivatosa and Milwaukee, in the county ot' Milwaukee and State of lllisconsin, have invented new and useful improvements in Protective Devices for Electric Circuits, ot which .the following is a t'ull, clear. conoise, and exact description, reference being had to the acompanying,r drawing, forming a part. of this specitication.I

This invention relates to, protective devices for electric circuits, and more particularly to protective devices involving a vaporizable electrical conductor which is liquid at working teniperatures.

ln a pat-ent of Erwin R. Stoeklei No 1,556,134, dated Uc-tober 6. 1925, is disclosed and claimed such a type ot protective de` vice having certain `features in common with that herein contemplated.

ln numerous installations the use oit a protective device 01 the character aforestated, adapted to provide both overload and underload protection, would be exceedingly desirable and the present invention has amongits objects that of providing such a device.

Another object is that of providing a unitary protective device having the characteristics last mentioned.

Another object is that 'ot providing such a device havingcertain elements thereet` so designed, constructed and arranged as ati'ord ari-exceedingly simplee compact and convenient structure.

Another object is that ot providing housing ot' such protective devices in an proved manner.

Other objects and advantages ivill 1ereinatter appear.

ln the accompanyfing` d. Wing,

Fig'. 1 is a vertical sect onal vienY tratiircT a preferred embodiment ol3 th vention, certain parts shown in from elevation and certain circuit connections oeine illustrated diagrannnaticallyj; While,

Fig. i2 a similar sectional viev,Y illustrating a moditied construction wherein cer tain elements more nearly resemble tac cor responding parts ot prior devices.,

Referring to Fie. l ot the drawing7 'the condilion'ot which control of the protected circuit is desired. is adapted under g'iven conditions ot overload to eil'cct 'aporization ot said liquid conductor for sudden interruption ot' the protected circuit. Moreover one ot said electrodes is capable of being moved out ot engagement with the liquid conductor and is biased to so move, while an under-load device serves, when energized above a `given critical value, to prevent such movement.

More speciiiallj.' the device as illustrated in Fig. 1 includes a support of molded insulatingr material or the like preferably cylindrical in shape. havinga multi-diameter bore (l to contain a liquid conductor 7, said bore havingY upwardlv facing annular shoulders S and 9 and 'the lower portion thercotl being materially constricted at l() substantiall);v as shoivn. fr cover plate 1l of like material and a bottoni plate 12 preterabl)v of asbestos lumber or the like are secured to the support prel'eial'il)v b v means of the bolts l?) as shown. said cover plate having a passage l-l and said bottom plate having a shouldered cvlini'lrical 'recess 15, both in substantial alinenient ivith the bore 6 of said support.

it llat electrode lit prcferabl)v circular in shape. is clamped betiveen the bottom plate l2 and the support in a manner to close 'the bore in the latter, \vher\,as, a similarly shaped shield 17 ot mica or other insulating material likewise clamped against the bottom ot said electrode 16. ln practice said electrode and said shield are preferably carried upon the. aforementioned annular shoulder of the bottom plate 12.

El lz t elec-tri -al heating element 18. which in practice may be either spiral. Zig zagr or ot other desired formation. is mounted below the shield 17 and Within the recess 15 ot the bottom plate. said heating element having a terminal ca ried Without said recess through a suitable opening and preferably attached.

to one of the bolts 13 as illustrated. The opposite terminal of `said heating device may be led .through a suitable opening in the shield 17- and spot welded, soldered or otherwise permanently electrically connected with the electrode 16 as shown, such construction being preferable in installations wherein said heating element and said elec-.i trode are to be connected in series.` Where said lelements are to be Yconnected in separate circuits, said' second terminal of the heating element is preferably led without the recess 15 and connected to the other of the'bolts 13 in the manner just described.

' A second electrode 19 is adapted to extend through the aforedescribed opening in the cover plate 11 and to project within the enlarged portion of the bore 6 of support 5, be-

' ing further adapted to reciprocate within said bore. The lower portion ofy said electrode is preferably enlarged, substantially as illustrated, and provided .with a down-4 vwardly facing fiat surface to co-operate with the upwardly facing shoulder 9 of said bore in the manner of a valve and its .seat for closure of said bore when said electrode is in its extreme downward position.

- The lower enlarged portion of said electrode is further provided with a restricted passage 2O servingto connect the constricted portion of the bore 6 with the region jabove the enlarged head of said electrode. Said constricted portion'l() of the bore 6 i`s filled with a liquid-conductor 7 which in practice may comprise metallic mercury, and which serves under normalconditions to connect electrically the aforedescribed electrodes. The enlarged portions of the bore 6 may in practice also contain a limited quantity of, the conductive fluid which, however, should under no conditions be permitted to attain thev level of the upper end of the passage'20. i The electrode 19 is adapted to extend a considerable distance above the cover plate ing` limb of the frame 21, said lever being arranged to project substantially horizontally forward from the frame 21 and being. adapted to act as an armature vfor attraction towardy the adj ac'ent end of the plug 22. The upper end ofthe electrode 19 is connected with an intermediate portion of said lever 26 by means of an insulating link 27 and 'a -pin 28 which is carried by said lever in a relation to project laterally beyond the coil 21 preferably 24. A spring 29 serves to bias the lever 26 and its connected parts to move upwardly, whereasthe-downward magnetic pull upon the lever 26 predominates the force .of said spring for all values of energization of'coil 24 above a given or predetermined value.

The coil 24 is connected in the circuit in accordance .withan electrical condition of which underload protection is desired and where saidcircuit is the same as that conjtrolled by the overload elements aforedescribed one coil terminal is preferably connected with an upper portion of the electrode 19 by means of a flexible lead 30 as shown. y f

In practice the support 5 is preferably secured upon a suitable panel 31 by meansA of an angle bracket 32 to which said support may be clamped by means of one of the bolts' 13 as illustrated. Furthermore the maghetic frame 21 is preferably provided with .outwardly bent feet such as that illustrated jat 33 for clamping said frame and its at,` tached parts to the same panel above the location of the support 5.4

Said panel .is-.preferably hinged upon a suitable switch box 34 to constitute the ldoor or cover therefor and is provided with asuitable slot 35through which the end of lever -26 is adapted to extend, said lever being preferably provided on the. outside o f said panel with a suitable insulating handle 36.

By the foregoing construction and ar rangement the switch parts are enclosed` within the boXwhen the cover 1s closed and moreover upon opening of said cover all of said parts are swung outwardly into a position affording ready and complete accessibility for calibration or inspection.

The operation of the device may be described as follows, the circuitconnections being assumed to .be those illustrated in Fig.v 1, that is to say, the heater, the overload circuit interrupting elements and the underload coil being all connected in series in the circuit to be protected. Under normal conl ditions the pull ofthe underload coil plus the effective weight of the partssubjected to such pull is sufficient to predominate the forceof the spring 29 formaintaining the electrode 19 in its extreme downward position and in contact with the liquid conductor .for maintaining circuit. However,

upon failure or given reduction of the ener# gization of said underload coil the force of the spring predominatcs and lifts the electrode 19 out of contact with the liquid conductor thereby interrupting the circuit.

Also under overload conditions of given magnitude and duration the heatercoil becornes energized to a degree sulicient tol effect vaporization of the liquid conductor located within the constriction 10, subject however, to an inverse time element due to Levi heat absorption by ine support- 5 and bottom plate 12. Thereupon the portion et the liquid conductor located above the region of vaporization is expelled upwardly through the passage 2 0 and such expulsion serves to et'fect sudden interruption of the controlled circuit. Such action obviously 'terminates the energization of the underload coil 24 whereupon again. the spring 29 acts to lift the electrode 19 to its extreme upper position and out ot contact withthe liquid conductor which latter is now free to return within -the constricted passage Q0 and to remain in its normal position.

Obviously following interruption ot' circuit under either of the` conditions aforedescribed the circuit may be re-established by a downward pull upon the lever QG such as to effect re-engagement ot the electrode 19 with the liquid conductor, and the circuit as thus completed will be maintained so long as normal conditions prevaildne to re-energization ot the nnderload coil 24.

Referring now to Fig. 2 ofthe drawing, the same illustrates a modified form of apparatus including parts possessing more marked structural analogy to those of the patent of Erwin R. Stoekle aforementioned.

In this instance an insulating base 5a serves as a support for the parts associated therewith, said base being provided with a multi-diameter bore having an intermediate constricted portion 1l):l and terminally located enlarged recesses and 41. A helical heating coil 18 is arranged within the recess 40 being retained by a body 42 of cement or the like. A tube 48 of glass or the like is arranged within said heating coil and adapted to terminate below the constriction 10a aforedescribed, said tube also being retained by the cement or the like. Vlhe bore within the support 5 is provided immediately above the constriction 10l with a dat annular shoulder 9a constituting in eltect a valve seat, while a valve shaped electrode 19 is adapted to co-operate with said seat Jfor closing said passage. The enlarged head ot said valve is also provided with a diagonally arranged passage 2O extending upwardly from the constricted passage 10,2L to the region above said valve head, all in the manner described in connection with Fig. .1.

A. suitable electrode 16a is secured within the lower end of the tube 43 preferably snbstantially as shown. and terminates within the heating coil 18a. ln practice the space within the tube 43 and also within the constricted portion ot the bore o is filled with a conductive piedinm T which is liquid at working temperatures. such liquid being `adapted normally to rise within the upper recess 41 ofthe support 5a to a level at all times materially lower than the upper ter minal of the passage 20. f

In this constrnctionthe magnetic frame 2l. is secured to the upper portion of the support 5 by bolts 44 or the like substan.

tially as shown, a washer of leather or the like being interposed to provide a liquid tight tit. Said trame 21 is provided with vertically alined and relatively enlarged openings to receive a magnetic tube 22a and also an insulating sleeve 23 said tube being ot' such length as to extend a considerable distance above the frame as show'n. An electromagnetic coil 24"1 having the usual end washers is mounted upon the sleeve 23 within the frame. spacing member 25 preferably of insulating material having a longitudinal bore 4G is arranged within the tube Q2 the latter being mounted so as to be attracted downwardly under the iniuence of the linx due to energization of said coil.

rl`he upper end of the electrode 19n is reduced and is adapted to extend longitudinally through and beyond said bore 46 ot the member being preferably secured to the latter and to the tube 22 b v means ot a pin 4T as illustrated. A washer 48 is located about the magnetic tube 22a above the trame whereas another washer 49 and a ter niinal device 50 are clamped upon the. upper end ot' the electrode 19nl by means of a nut 51, while a suitable knob or button 53 is also threaded upon the projecting end of said elect-rode.

A helical spring 54 is arranged between the washers ai'oredescribed and serves to bias the aforedescribed reciprocable parts upwardly` said spring being of reduced power such as to be predominated by the electromagnetic pull during energization of the coil 24 above a predetermined value, whereby the valve is maintained seated against the action ot said spring. However, it' at any time the cnergization of the coil t'alls below such predetermined valne .the force of the spring predominates for lifting its associated parts including the electrode 19tl which is thus elevated ont ot' engagement with the liquid conductor, thereby interrupting the controlled circuit in response to the aforementioned reduction in energization of the coil 24.

As illustrated, the heating coil and the nnderload coil are connected in series in the circuit which is to be protected` the liquid conductor and its associated electrodes. however, being connected in a diti'erent circuit, in this instance, the energizing circuit of the switch which controlla Ythe protected circuit.

The operationA of the complete device is in all material respects similar to that of the. aforedescrilied construction.

As is apparent from Vthe relative size of corresponding parts ot the two devices attoredescribed, the type employing the fiat heatn ing element .intimately associated with a eo'rjecting said liquid conductor `to a heating effect for interruption of circuit betweenA said electrodes under given conditions and means to automatically effect relative movement-of said electrodes for interrupting circuit therebetween under other conditions.

2. A protective device forelectric circuits comprising a conductor which is liquid at working temperatures, relatively movable electrodes to be electrically connected by said conductor, means to effect relative movement of saidl electrodes for interruption of circuit `therebetween and means to effect interruption of circuit between said `electrodes byhcating of said liquid conductor and to further effect operation 'of said `meansyr Yrelative movement of said electrodes to prevent re-establishment of circuit therebetweeixgnpon restoration of said liquid Vconductor to 'tsnormal state.

3. A protective'device vfor electric circuits, comprising alconductor which is liquid at working temperatures, relatively #movable electrodes to be connected thereby, said electrodes requiring restraint in a given relation for connection thereof by said conductor and means tdA so restrain said electrodes subject to release upon interruption of the continuity .of said vliquid conductor.

4. vA protective device for electric'circuits, comprising a conductor which is liquid at working temperatures, relatively movable electrodes to be connected thereby, said elec# trodes requiring restraint in a given relation forconnection thereof by said conductor,

.means to so restrain said electrodes subject to release upon interruption of the circuit therethrough, and means subjecting said liquid conductor to thermal influence to in terrupt the-circuit between said electrodes automatical'iy under given conditions.

5. In a protective device for electric circuits,` the combination with a conductor which is liquid at working temperatures, electrodes providing circuit connections for said conductor, and ineansto vaporize and expel liquid of said conductor from between said electrodes for interrupting circuit, certain of said electrodes being movable to provide for return of the-expelled fluid and means for so moving said certain of said lelectrodes and at the same time withdrawing the same out of contact with the fluid t0. maintain the circuit interrupted pending voluntary reclosure.

6. In a protective device for electric circuits, the combination with a conductor which is liquid at working temperatures, electrodes providing circuit connections for sai-d conductor, and overload means to vaporize li uid of said conductor for interrupting circuit between said electrodes, one

of 's'aid electrodes being movable to provide for' restoration of continuity ot said conductor, means tending to effect such movementorI said -`electrode and normally preponderant electro-responsive means opposing such movement of said electrode.

7. In a protective device for electric circuits, the combination with 'a conductor which lis liquid at working temperatures, electrodes providing circuit connections for said conductor, and overload means lto vaporize'liquid of saidv conductor for inter rupting circuitbetween said electrodes,"one of said electrodes being movable out of contact with said conductor, means tending to so move said electrode and means for holding said electrode against such movement unde-r all conditions of energization, above a given value, of the circuit to be protected, subject to release and consequent movement of said electrode under lesser degrees pf ener.- gization of said circuit.

8. A protective device for electric circuits, comprising electro-responsive means for interrupting circuit under given conditions of overload andunderload selectively, said means including a vaporable conductor which is liquid at working temperatures.

9. A protective device for electric circuits comprising relatively movable electrodes, a conductor which is liquid at working temperatures connecting said electrodes, means for displacing a portion of said conductor to break'the circuit under vpredetermined overload conditions, and co-operatin electro-responsive means adapted to bres. said circuit under ditions.

10. A protective device for electric circuits comprising relatively movable electrodes, a.

vconductor which is liquid at working tempredetermined underload conperatures interposed between said electrodes,

ciated circuit, comprising a conductor which is liquid at working temperatures, insulating means providing a' column of said conductor,

electrodes to bein 'contact with terminal portions of lsaid column respectively, thermoelectric means to veiect vaporiaationand consequent displacement of liquid of said con- .ductor under. givenconditionsof overload for, interrupting circuit-between said 'electrodes, one of said electrodesbeing rnovable 'out-,of contact with said liquidiconductor, a

spring tending so to .move-said electrode, and:

an underload coil` adapted to prea'fent 'such movement of said electrode Aunder normalv 15 i ,Y

conditions. f i

12. vA 'circuitl interrupter comprising a tubular base, spaced electrodes and 'a connecting liquid conductor carried by said base, one of said electrodes being movable with respect to said base and being provided vwith an internal passage and an associated valve to lco-vop erat e with a seat provided` on said base, a heating element to vaporize and displace liquid of saidl conductor between said electrodesfor causing an upward flow 'of fluid of said conductor through` said pasv sage for interruption of circuit between said electrodes, said passage being arranged to prevent return of liquid therethrough, said E valve vbeing voluntarily operable to permit return of the displaced fluid and said latter electrode being movable out of engagement with said. liquid conductor, electro-magnetic meansto're'si'stsuch movement of said elecrupting circuit between said f electrodes,

means including an electro-magnetic` frame and an operating lever, to act upon one of said electrodes for interrupting such circuit under 'given underload conditions, a switch box to contain said parts,said boX having a v hinged cover panel and means for securing said base and said frame to the inner side" of said panel to swing therewith Wout of said box, said panel having an opening permitting said lever to protrude from said box.

In Witness whereof, we have hereunto subscribed our names.

THOMAS E. BARNUM nRwiN R. sToEKLn. 

